That is fine if you always are swapping. However if you normally charge at home that becomes a big deal - if your current battery wears out/fails because it has 500,000k miles on it are you out a new one? Do you pay for the tow to get to a swap station? Again, if everyone always swapped this would be easy to amortize and not a problem but the mixed use.

Of course this isn't a new problem. I know people who own their own welding gas tank - but they always swap the tank out. The place they swap at somehow handles when the tank needs to be re-certified - and people don't ask questions.